`isinstance-second-argument-not-valid-type` does not handle `Enum.enum`

[jeromeag]

Bug description

"""just to test pylint isinstance-second-argument-not-valid-type"""
from enum import Enum

Direction = Enum('Direction', ['LEFT', 'RIGHT', 'BOTH'])

def check_direction(direction):
    """just to test pylint isinstance-second-argument-not-valid-type"""
    if not isinstance(direction, Direction):
        raise TypeError(f'Not a RUKind ("{direction}" is a {type(direction)})')

Command used

poetry run pylint a.py

Pylint output

************* Module a
a.py:8:11: W1116: Second argument of isinstance is not a type (isinstance-second-argument-not-valid-type)

------------------------------------------------------------------
Your code has been rated at 8.00/10 (previous run: 6.00/10, +2.00)

Expected behavior

---

Your code has been rated at 10.00/10 (previous run: 8.00/10, +2.00)

Pylint version

pylint 2.16.2
astroid 2.14.2
Python 3.9.10 (main, Jan 20 2022, 21:37:52) 
[GCC 11.2.0]

OS / Environment

Cygwin
Poetry (version 1.3.2)

[nickdrozd]

The isinstance-second-argument-not-valid-type cannot handle enums correctly at all. Besides the false positive reported here, it also exhibits false negatives. Consider this code:

from enum import Enum

Direction = Enum('Direction', ['Left', 'Right', 'Both'])

# False positives
print(isinstance(0, Direction))
print(isinstance(Direction.Left, Direction))

# False negatives
print(isinstance(0, Direction.Left))
print(isinstance(Direction.Left, Direction.Left))

The first two isinstance calls are flagged, but they shouldn't be, since they run fine. The second pair of calls are not flagged, but they should be, since they fail at runtime.